Application of calcium-to-phosphorus (Ca/P) ratio in the diagnosis of pseudohypoparathyroidism: another piece in the puzzle of diagnosis of Ca-P metabolism disorders.

Objective: The serum calcium (Ca)-to-phosphorus (P) ratio has been proposed to identify patients with primary hyperparathyroidism and chronic hypoparathyroidism (HPT), but it has never been tested in pseudohypoparathyroidism (PHP). The aim of this study was to test the performance of Ca/P ratio in PHP diagnosis compared with that in healthy subjects and patients with HPT for differential diagnosis. Design: A retrospective, cross-sectional, and observational study was carried out. Methods: Serum Ca, P, creatinine, parathyroid hormone (PTH), and albumin were collected. Ca and P were expressed in mmol/L. Ca/P diagnostic performance was evaluated by receiver operating characteristic curve, sensitivity, specificity, and accuracy. Results: A total of 60 patients with PHP, 60 patients with HPT, and 120 controls were enrolled. The Ca/P ratio was lower in patients with PHP and HPT than that in controls (p < 0.0001). The cutoff of 1.78 (2.32 if Ca and P measured in mg/dL) for Ca/P ratio could identify patients with PHP and HPT among the entire cohort (sensitivity and specificity of 76%). No valid cutoff of Ca/P was found to distinguish patients with PHP from patients with HPT; in this case, PTH above 53.0 ng/dL identified patients with PHP (sensitivity and specificity of 100%). The index (Ca/P × PTH) above 116 ng/L recognized patients with PHP from controls (sensitivity of 84.7% and specificity of 87.4%), whereas (Ca/P × PTH) below 34 ng/L recognized patients with HPT from controls (sensitivity of 88.9% and specificity of 90.8%). Conclusions: The Ca/P ratio below 1.78 (2.32 CU) is highly accurate to identify patients with PHP and HPT, although it is not reliable to differentiate these two conditions. The index (Ca/P × PTH) is excellent to specifically recognize PHP or HPT from healthy subjects.

How Much Vitamin D is Too Much? A Case Report and Review of the Literature.

BACKGROUND: The beneficial effects of vitamin D, together with the high prevalence of vitamin D deficiency, have led to an expanding use of vitamin D analogues. While inappropriate consumption is a recognized cause of harm, the determination of doses at which vitamin D becomes toxic remains elusive. CASE PRESENTATION: A 56-year woman was admitted to our Hospital following a 3-week history of nausea, vomiting, and muscle weakness. The patient had been assuming a very high dose of cholecalciferol for 20 months (cumulative 78,000,000UI, mean daily 130,000UI), as indicated by a non-- conventional protocol for multiple sclerosis. Before starting vitamin D integration, serum calcium and phosphorus levels were normal, while 25OH-vitamin D levels were very low (12.25 nmol/L). On admission, hypercalcemia (3.23 mmol/L) and acute kidney injury (eGFR 20 mL/min) were detected, associated with high concentrations of 25OH-vitamin D (920 nmol/L), confirming the suspicion of vitamin D intoxication. Vitamin D integration was stopped, and in a week, hypercalcemia normalized. It took about 6 months for renal function and 18 months for vitamin D values to go back to normal. CONCLUSION: This case confirms that vitamin D intoxication is possible, albeit with a high dose. The doses used in clinical practice are far lower than these and, therefore, intoxication rarely occurs even in those individuals whose baseline vitamin D serum levels have never been assessed. Repeated measurements of vitamin D are not necessary for patients under standard integrative therapy. However, patients and clinicians should be aware of the potential dangers of vitamin D overdose.

Crosstalk between gonadotropins and thyroid axis.

Gonadotropins and thyroid hormones are essential, respectively, for reproduction and metabolism. The classical endocrinological approach is based on the detection of axes that start from the hypothalamus and arrive at the final effector organ, in this case gonads and thyroid. However, several clues suggest that these axes do not work in parallel, but they dialogue with each other. In this article, we review evidences demonstrating crosstalk between gonadotropins and thyroid axis. Firstly, there is an undeniable structural similarity of both hormones and receptors, maybe due to a common ancient origin. This structural similarity leads to possible interaction at the receptor level, explaining the influence of thyroid stimulating hormone on gonadal development and vice versa. Indeed, altered levels of thyroid hormones could lead to different disorders of gonadal development and function throughout entire life, especially during puberty and fertile life. We here report the current knowledge on this item both in males and in females. In particular, we deepen the interaction between thyroid and gonads in two situations in females: polycystic ovary syndrome, the most frequent cause of menstrual alteration, and pregnancy.